wrapper.go: Use two viper instances to watch configs

Also make sure that the config from the config file is merged, so we
don't miss the custom resource state config file defined in the options
config.

internal/wrapper.go

@@ -19,12 +19,13 @@ package internal
 import (
 	"context"
 	"errors"
+	"os"
 	"path/filepath"
-	"sync"
 	"time"
 
 	"github.com/fsnotify/fsnotify"
 	"github.com/spf13/viper"
+	"gopkg.in/yaml.v3"
 	"k8s.io/klog/v2"
 
 	"k8s.io/kube-state-metrics/v2/pkg/app"
@@ -43,96 +44,58 @@ func RunKubeStateMetricsWrapper(opts *options.Options) {
 
 	ctx, cancel := context.WithCancel(context.Background())
 	if file := options.GetConfigFile(*opts); file != "" {
-		viper.SetConfigType("yaml")
-		viper.SetConfigFile(file)
-		if err := viper.ReadInConfig(); err != nil {
+		cfgViper := viper.New()
+		cfgViper.SetConfigType("yaml")
+		cfgViper.SetConfigFile(file)
+		if err := cfgViper.ReadInConfig(); err != nil {
 			if errors.Is(err, viper.ConfigFileNotFoundError{}) {
 				klog.ErrorS(err, "Options configuration file not found", "file", file)
 			} else {
 				klog.ErrorS(err, "Error reading options configuration file", "file", file)
 			}
 			klog.FlushAndExit(klog.ExitFlushTimeout, 1)
 		}
-		viper.OnConfigChange(func(e fsnotify.Event) {
+		cfgViper.OnConfigChange(func(e fsnotify.Event) {
 			klog.Infof("Changes detected: %s\n", e.Name)
 			cancel()
 			// Wait for the ports to be released.
 			<-time.After(3 * time.Second)
 			ctx, cancel = context.WithCancel(context.Background())
 			go KSMRunOrDie(ctx)
 		})
-		viper.WatchConfig()
-	}
+		cfgViper.WatchConfig()
 
+		// Merge configFile values with opts so we get the CustomResourceConfigFile from config as well
+		configFile, err := os.ReadFile(filepath.Clean(file))
+		if err != nil {
+			klog.ErrorS(err, "failed to read options configuration file", "file", file)
+		}
+
+		yaml.Unmarshal(configFile, opts)
+	}
 	if opts.CustomResourceConfigFile != "" {
-		WatchConfig(opts.CustomResourceConfigFile, func(e fsnotify.Event) {
+		crcViper := viper.New()
+		crcViper.SetConfigType("yaml")
+		crcViper.SetConfigFile(opts.CustomResourceConfigFile)
+		if err := crcViper.ReadInConfig(); err != nil {
+			if errors.Is(err, viper.ConfigFileNotFoundError{}) {
+				klog.ErrorS(err, "Custom resource configuration file not found", "file", opts.CustomResourceConfigFile)
+			} else {
+				klog.ErrorS(err, "Error reading Custom resource configuration file", "file", opts.CustomResourceConfigFile)
+			}
+			klog.FlushAndExit(klog.ExitFlushTimeout, 1)
+		}
+		crcViper.OnConfigChange(func(e fsnotify.Event) {
 			klog.Infof("Changes detected: %s\n", e.Name)
 			cancel()
 			// Wait for the ports to be released.
 			<-time.After(3 * time.Second)
 			ctx, cancel = context.WithCancel(context.Background())
 			go KSMRunOrDie(ctx)
 		})
+		crcViper.WatchConfig()
 	}
 	klog.Infoln("Starting kube-state-metrics")
 	KSMRunOrDie(ctx)
 	select {}
 }
-
-// WatchConfig is taken and adapted from https://github.com/spf13/viper/blob/b89e554a96abde447ad13a26dcc59fd00375e555/viper.go#L429 MIT-Licensed
-func WatchConfig(filename string, onConfigChange func(fsnotify.Event)) {
-	initWG := sync.WaitGroup{}
-	initWG.Add(1)
-	go func() {
-		watcher, err := fsnotify.NewWatcher()
-		if err != nil {
-			klog.ErrorS(err, "Failed to create new watcher")
-		}
-		defer watcher.Close()
-
-		// we have to watch the entire directory to pick up renames/atomic saves in a cross-platform way
-		configFile := filepath.Clean(filename)
-		configDir, _ := filepath.Split(configFile)
-		realConfigFile, _ := filepath.EvalSymlinks(filename)
-
-		eventsWG := sync.WaitGroup{}
-		eventsWG.Add(1)
-		go func() {
-			for {
-				select {
-				case event, ok := <-watcher.Events:
-					if !ok { // 'Events' channel is closed
-						eventsWG.Done()
-						return
-					}
-					currentConfigFile, _ := filepath.EvalSymlinks(filename)
-					// we only care about the config file with the following cases:
-					// 1 - if the config file was modified or created
-					// 2 - if the real path to the config file changed (eg: k8s ConfigMap replacement)
-					if (filepath.Clean(event.Name) == configFile &&
-						(event.Has(fsnotify.Write) || event.Has(fsnotify.Create))) ||
-						(currentConfigFile != "" && currentConfigFile != realConfigFile) {
-						realConfigFile = currentConfigFile
-						if onConfigChange != nil {
-							onConfigChange(event)
-						}
-					} else if filepath.Clean(event.Name) == configFile && event.Has(fsnotify.Remove) {
-						eventsWG.Done()
-						return
-					}
-
-				case err, ok := <-watcher.Errors:
-					if ok { // 'Errors' channel is not closed
-						klog.ErrorS(err, "Watcher received an error")
-					}
-					eventsWG.Done()
-					return
-				}
-			}
-		}()
-		watcher.Add(configDir)
-		initWG.Done()   // done initializing the watch in this go routine, so the parent routine can move on...
-		eventsWG.Wait() // now, wait for event loop to end in this go-routine...
-	}()
-	initWG.Wait() // make sure that the go routine above fully ended before returning
-}